Metallothionein mRNA in monocytes and peripheral blood mononuclear cells and in cells from dried blood spots increases after zinc supplementation of men

A specific, sensitive and reliable index for assessment of human zinc statu s has not been developed, and continues to present a considerable challenge for nutritionists in the trace element field. We have focused on metalloth ionein (MT) expression as a potential index. A protocol involving 16 men an d a 10-d supplementation period plus a 4-d postsupplementation period was u sed to examine the relative response of MT expression in erythrocytes, mono cytes, peripheral blood mononuclear cells (PBMC) and cells from a dried blo od spot (DBS). Zinc was supplemented at the current adult male recommended dietary allowance (RDA) of 15 mg. Erythrocyte MT protein, as measured by EL ISA, increased gradually to about twofold over the placebo group during zin c supplementation and remained elevated for 4 d postsupplementation. Compet itive reverse transcriptase-polymerase chain reaction showed that MT mRNA l evels in both monocytes and PBMC increased (up to 4.7- and 2.7-fold, respec tively) after 2 d of supplementation, with greater expression in monocytes compared with PBMC. Total RNA extracted from dried blood spots, representin g cells from 50 mu L of blood, showed a comparable change in MT mRNA upon z inc supplementation. In each leukocyte population isolated, when zinc suppl ementation was withdrawn, MT mRNA levels decreased. Collectively, these exp eriments show that, in men, MT gene expression increases during supplementa tion at the RDA, and that the DBS sampling method will be of value in measu ring MT expression in a variety of clinical and survey situations.